Energy conversion systems are known that can obtain power from varying environmental conditions such as from sea waves by using the waves to move parts repeatedly back and forth.
Applicant's U.S. Pat. No. 7,632,041 discloses a system for generating electrical power from waves, where an electricity-generating stretchable material (SM) is coupled to a static part and to a displaceable part that move with the waves. The SM material functions like a variable capacitor. As a part of the system is moved back and forth, it can be made to repeatedly stretch and relax a quantity (e.g. a sheet) of SM which is preferably EAP (electro active polymer) material. A pair of electrodes lies against the opposite surfaces of a sheet of SM material to create a capacitor, and an electrical charge is applied to the pair of electrodes. When the sheet is stretched, the surface is increased while at the same time the distance between its opposite surfaces is decreased. As a result, the capacitance between its pair of electrodes increases, and the voltage resulting from the charge on its electrodes decreases. Conversely, when a stretched sheet of SM material is partially relaxed, its capacitance decreases and the voltage between the electrodes lying at its opposite surfaces, increases. Electrical power is drawn from a capacitor consisting of pair of electrodes that lie on opposite sides of a relaxing SM sheet, by flowing out the charge (between its pair of electrodes). When the SM sheet is stretched again so the voltage decreases, an electrical charge is again flowed (as current) to the electrodes to recharge them, so the charge can flow out when the voltage has increased again. The fact that electricity flows out of the pair of electrodes (they are discharged) that are at a higher voltage than the voltage at which the electrodes are recharged, results in obtaining power from the system.
The need to repeatedly recharge the electrodes that lie on opposite surfaces of a SM sheet, results in the need for an electrical source that supplies current at the required recharge voltage (e.g. 2500 volts) at the proper times in each cycle of operation. This can require AC/DC conversions and voltage step ups or step downs, which result in power losses that can greatly reduce the efficiency of the energy conversion system. A system that used an internal source for recharging a pair of electrodes could have a greatly increased efficiency. Such a system should be capable of extracting energy from the environment like sea waves, currents or waterflows, using a relatively simple construction.